HELP!!!!!!!! cake carving

AHi all
I'm new to cake carving and everywhere I read it suggests freezing the cake and wrapping it in cling film to keep the freshness in, but how long does it have to be in the freezer for? I am doing a trial run on a big cake I need to do in September?

I never freeze my cakes before carving, If something's going to shift and fall off I want to know that when I'm working on it! If it's frozen and thaws, things that are carved out might not stay supported the same way when they're thawed as when they're frozen.